Method for manufacturing cathode ray tube screen

ABSTRACT

In producing the phosphor screen of a cathode ray tube, particularly a color picture tube or kinescope, by coating the surface of a face plate with a light sensitive layer containing phosphor material and then exposing such layer to light passing through the apertures of a mask from a light source, the position of the light source relative to the face plate is varied during the exposure in a direction which is parallel to a line perpendicular to the face plate at the center of the latter.

United States Patent [i9] Inoue Dec. 24, 1974 METHOD FOR MANUFACTURING CATHODE RAY TUBE SCREEN [75] Inventor: Takuji lnoue, Fujisawa, Japan [73] Assignee: Sony Corporation, Tokyo, Japan [22] Filed: Sept. 15, 1972 [21] App]. No.: 289,445

[30] Foreign Application Priority Data Sept. 21, 1971 Japan 46-73565 [52] US. Cl. 96/361, 96/27 E, 313/92 B,- 354/1 [51] Int. Cl G03c 5/00 [58] Field of Search 96/36.1, 27 E; 95/1 R;

[56] 5 References Cited UNITED STATES PATENTS 3,667,947 6/1972 McKee'l- .-96/36.1

6/1972 Robinder et al. 96/3 61 3,685,994 8/1972 Frey 96/36.l 3,725,]06 4/1973 Hosokoshi 313/92 B 3,767,395 10/1973 Rowe et al 96/36.l 3,767,396 l0/l973 Kaplan 96/36.l

Primary Examiner-Ronald H. Smith Assistant Examiner-Edward C. Kimlin Attorney, Agent, or Firm-Lewis H. Eslinger; Alvin Sinderbrand [57] 9 ABSTRACT in producing the phosphor screen of a cathode ray tube, particularly a color picture tube or kinescope, by coating'the surface of a'face plate with a light sensitive layer containing phosphor material and then exposing such layer to light passing through the apertures of a mask from a light source, the position of the light source relative to the face plate is varied during the exposure in a direction which is parallel to a line perpendicular to the face plate at the center of the latter.

11 Claims, 12'Drawing Figures (PR/0R AR 7") 1Z0 PATENTED 3.856525 SHEET 10F 5 (PRIORART) ET. 3

SHEET 2 BF 5 PATENTED M824 1974 SHEET 5 BF 5 m w m m a w mgkmafi Us NERQIEWQ This invention relates generally to cathode ray tubes, and more particularly is directed to the manufacture of the phosphor screens of color picture tubes or kinescopes.

The phosphorscreen of a color picture tube or kinescope is made up of cathodoluminescent phosphors respectively having blue, green andred emissions and being deposited on elemental areas of the surface of the face plate of the tube, which elemental areas are arranged in triads associated with respective apertures of a shadow grid or mask disposed adjacent to the phosphor screen. In the conventional optical printing method for producing the phosphor screen, the shadow grid or mask which will eventually be associated with the phosphor screen in a completed color picture tube or kinescope is used as the optical mask through which each light sensitive layer containing cathodoluminescent phosphor material having emissions of a predetermined color is exposed to light from alight source in a respective fixed position that generally corresponds to'the deflection center of the respective electron beam in the completed color picture tube. After such exposure of each light sensitive layer, the latter is developed so that therespective phosphor material remains permanently only on selected areas of the face plate surface. In color picture tubes, it is desirable that the apertures of the shadow grid or mask by progressively decreased in size from maximum, dimensions at the center of the phosphor screen to minimum dimensions adjacent the edges of the screen while the corresponding dimensions of the elemental areas of the different color phosphors are substantiallyuniform over the entire extent of the screen in order to ensure that there'will be an adequate tolerance for the correct landing of the electron beams on the respective color phosphors particularly at the edge portions of the screen. In the conventional optical printing method, the elemental areas of the different color phosphors are provided with uniform sizes over the entire extent of the phosphor screen, even though the apertures of the shadow grid or mask'decrease in size from the center toward the edges of the mask, by varying the intensity of the light to which the central and edge portions of each light sensitive layer are exposed, that is, by employing a light filter between the light source and the mask which varies the intensity of the light passing through the apertures of the mask generally in inverse proportion to the sizes of the apertures. However, the foregoing conventional method for optically printing the phosphor screen of a color picture tube is disadvantageous in that the elemental areas of the different color phosphors do not have the desired sharp definition, particularly at the edge portions of the screen, and further in that it is necessary to employ a light source having a very large light so that the latter will havea relatively large tolerance for the landing of the electron beams thereon particularly at the edge portions of the screen.

Another object is to provide an improved method for optically printing the phosphor screen of a color picture tube, as aforesaid, and by which the elemental areas of the different color phosphors have uniform dimensions and are sharply and precisely defined over the entire area of the screen.

Still another object is to provide an improved method for optically printing the phosphor screen of a color picture tube, as aforesaid, and which permits the use of a light source having a relatively low light energy output or relatively shorter exposure times for the exposure of the light sensitive layers.

In accordance with an aspect of this invention, each light sensitive layer coated on the surface of the face plate during the optical printing of the phosphor screen of a color picture tube is exposed to light passing through the apertures of a shadow grid or mask from a light source which,-in the course of such exposure of the layer to the light, is disposed at least at two positions relative to the face plate which are spaced from each other in a direction parallel to a line perpendicular to the face plate at the center of the latter. Of course, in the optical printing of the phosphor screen of a color picture tube in accordance with this invention, the at least two positions occupied by the light source during the exposing of each light sensitive layer containing cathodoluminescent phosphor material having emissions of a predetermined respective color are displaced, in a direction parallel to the surface of the face plate, from the at least two positions of the light source used for exposing each of the other light sensitive layers.

The above, and other objects, features and advantages of this invention, will be apparent in the following detailed description of illustrative embodiments of the invention which is to be read in connection with the accompanying drawings, wherein:

FIG. I is a schematic view illustrating the optical printing of the phosphorscreen of a color picture tube according to the conventional'met hod heretofore employed;

FIG. 2 is a plan view of the shadow grid of a color picture tube which may be employed as a mask during the optical printing method of FIG. 1;

FIGS. 3 and 4 are graphical representations of the light energy distributions obtained at the central and edge portions, respectively, of a light sensitive layer during the optical printing of the phosphor screen in accordance with the conventional method;

FIG. 5 is a schematic view similar to that of FIG. 1, but illustrating the optical printing method in accordance with an embodiment of the present invention;

FIGS. 6 and 7 are enlarged, fragmentary schematic sectional views illustrating the manner in which the light sensitive layer is exposed to light at its central and edge portions, respectively, when using the optical printing method according to this invention;

FIGS. 8 and 9 are graphical representations of the light energy distributions obtained at the central and edge portions of the light sensitive layer when exposed to light in the manner indicated on FIGS. 6 and 7, respectively;

FIG. It) is a schematic sectional view illustrating an apparatus for the optical printing of the phosphor screen of a color picture tube in accordance with this invention;

FIG. 11 is a schematic plan view of another form of shadow grid or mask that can be used in a color picture tube having its phosphor screen optically printed in accordance with this invention; and

FIG. 12 is a graphical representation showing the increase in the size of the elemental area of each phosphor at various locations on the phosphor screen in response to light source movement during the exposure step of the optical printing method in accordance with this invention.

Referring to the drawings in detail, and initially to FIG. 1 thereof, it will be seen that, in the conventional method for optically printing the phosphor screen on the face plate 2 of a color picture tube or kinescope, the inner surface of face plate 2 is coated with a layer 1 of a light sensitive substance, wuch as polyvinyl alcohol, containing cathodoluminescent phosphor material having emissions of a predetermined color. The layer 1 may be applied as a slurry of the phosphor material in the light sensitive substance, or the light sensitive substance may be first coated on face plate 2 and then, while the light sensitive substance is still moist, the phosphor material may be sprayed thereagainst. An optical mask 3, which is preferably the shadow grid or mask to be associated with the phosphor screen in the completed color picture tube, is positioned adjacent the face plate 2 so that light sensitive layer 1 on the face plate will be exposed to light passing through apertures of the mask 3 from a light source 4. interposed between the light source 4 and the mask 3 are a corrective lens 5 and an optical filter 6 which, as hereinafter described, may be formed to vary the relative intensities of the light to which the light sensitive layer 1 is exposed at its central and edge portions, respectively. During the exposure of light sensitive layer 1 to light from source 4, the latter is maintained in a fixed position which approximately corresponds to the deflection center of the electron beam produced in the completed color picture tube for energizing the phosphor material in layer 1. Thus, only selected areas of layer 1 are exposed to light passing through the apertures of mask 3 and, at the completion of such exposure, layer 1 is suitably developed to harden those areas that have been exposed and to remove the remaining portions of such layer. The foregoing steps are repeated with a second light sensitive layer containing cathodoluminescent phosphor material having emissions of another color, and with the light source 4 being disposed, during exposure of the second light sensitive layer, at a fixed position which is displaced, in a direction parallel to the face plate surface, from the position of the light source used during exposure of the first layer so as to correspond to the deflection center of the electron beam for energizing the phosphor material of the second layer. Thus, cathodoluminescent phosphors having different color emissions, for example, red, green and blue emissions, are deposited on elemental areas of the surface of face plate 2, for example, on dot-like or stripe-like areas of such surface, and which are arranged in triads each corresponding to an aperture of mask 3.

Referring now to FIG. 2, it will be seen that in the case of color picture tubes having a phosphor screen with its different color phosphors arranged in parallel stripe-like areas, the shadow grid 9 associated with such phosphor screen may include upper and lower frame members 7 having parallel, spaced apart grid elements 8 extending therebetween to define parallel elongated apertures 10 between the grid elements. In grid mask 9, the widths of the elongated apertures 10 are shown to decrease progressively from a maximum width W at the center of mask 9 to minimum widths W at the opposite sides or edges of the mask. When the grid mask 9 having the widths of its elongated apertures 10 varied, as aforesaid, is employed in connection with a phosphor screen having its different color phosphors in stripe-like areas that are of substantially uniform width over the entire extent of the phosphor screen, a desirably large tolerance for the landing ofthe electron beams on the respective stripe-like color phosphors is obtained, particularly at the opposite side or edge portions of the screen. However, if the shadow grid 9 of FIG. 2 is employed as the optical mask 3 during the optical printing of the phosphor screen by the conventional method described above with reference to FIG. 1, difficulties are experienced in ensuring that the stripe-like color phosphors obtained in correspondence to the relatively narrow apertures 10 adjacent the side edge portions of shadow grid 9 will have substantially the same widths as the Stripe-like color phosphors obtained in correspondence to the relatively wide apertures 10 at the center of shadow grid 9.

In order to substantially equalize the widths of the stripe-like areas of the several color phosphors resulting from the exposure of the respective light-sensitive layers to light passing through the relatively wide elongated apertures10 in the central portion of mask 9 and the relatively narrow elongated apertures 10 in the edge portions of such mask, the optical filter 6 employed in the conventional optical printing method is designed to substantially diminish the intensity of the light transmitted through the central portion of the filter as compared with the intensity of the light transmitted through the edge portions of the filter. Thus, for example, the filter 6 may be formed of a glass or other transparent plate having chromium non-uniformly evaporated or sputtered on a surface thereof so that the resulting layer of evaporated chromium is relatively thick or dense at the central portion of the filter and progressively decreases in thickness or density toward the edges of the filter plate.

With the above described filter 6 employed in the conventional optical printing method, during exposure of each light sensitive layer, different distributions of light energy act on the light sensitive layer at regions of the latter corresponding to relatively wide and narrow apertures at the central and edge portions, respectively, of the mask, for example, as represented by the curves 1 and II on FIGS. 3 and 4, respectively. More specifically, at the central portion of the mask 3 where the apertures are relatively wide, the intensity of the light passing therethrough from the filter 6 is relatively reduced so that the curve I representing the light energy distribution on the corresponding region of the light sensitive layer has a relatively low maximum value at its center and decreases relatively gradually toward the opposite sides of the center, as shown on FIG. 3. If the threshold of the minimum light energy required for hardening the light sensitive layer is as indicated at a on FIG. 3, then it is apparent that the light sensitive layer will be hardened over the width S which corresponds to the width of the area at which the respective phosphor material will bepermanently retained upon the threshhold light energy a,,, the limits or edges of the area on which the respective phosphor material will be permanently retained, upon development of the light sensitive layer, are sharply and smoothly defined. On the other hand, as shown on FIG. 4, the light of relatively high intensity passing through an edge portion of filter 6 and through a relatively narrow aperture in an edge portion of mask 3 provides a light energy distribution on the respective region of the light sensitive layer which is represented by the curve II having a relatively higher maximum value at its center than the curve I, but falling off more quickly at the opposite sides ofthe center of the curve. Since the light energy distribution curve II is above the threshhold light energy a,, over the width S, which is approximately the same as the width S on FIG. 3, the areas of the surface of face plate 2 at which vthe'phosphor material 'is permanently retained upon development of the light sensitive layer willbe approximately the same at the edge portions as at the central portion of the face plate. However, as shown on FIG. 4, the slope of the curve II at the level of the threshhold of light energy a, is relatively small, as compared'with the steep slope of curve I at the level of the threshhold light energy a,,, so that the edges of the areas at which the phosphor material is permanently retained on the edge portions of the face plate are not sharply I defined and, at times, may be wavy or irregular. Further, in order, to obtain the large difference between the peak values of the light energy distributions II and I at the edge and central portions, respectively, that are necessary for equalizing the widths of the areas at which the phosphor material is permanently retained upon development of the light sensitive layer, it is necessary either to employ a light source d having a very large light energy output or to use an undesirablylong exposure time. i

Generally, the present invention avoids the above described disadvantages of the conventional optical method for producing the phosphor screen of a color picturetube or kinescope which is to be associated with a shadow grid or mask having apertures which decrease in size from the central portion to the edge portions of the mask, merely by disposing the light source, during the exposure of each light sensitive layer, at least at two positions relative to the face plate and mask, which positions are spaced from each other in a direction parallel to a line perpendicular to the face plate at the center of the latter. Thus, as shown more particularly on FIG. 5, in the method according to this invention for optically printing a phosphor screen on the face plate ll of a color picture tube, each light sensitive layer 12 coated on the-surface of face plate llll'and having conventional constituents is exposed to light passing through the apertures 13a of the shadow grid or mask 13 after passing through a correction lens 14 and optical filter 15 from a light source 116 which, in the course of the exposing of the layer 12 to light from the source 16, is disposed at least at two positions Z and Z relative to the face plate Ill and mask 13, which two positions Z, and Z, are spaced from each other in the direction Z-Z parallel to a line perpendicular to face plate ll at the center of the latter.

It will be apparent that, in disposing light source In at least at the two positions Z, and 2, relative to face plate 11 and mask l3 during the exposure of each light sensitive layer lll, either the light source 16 can be moved in the direction ZZ while face plate 11 and mask 13 remain stationary, or light source 16 can remain fixed while face plate ll and mask 13 are moved, as a unit, relative to the fixed light source in the direction Z--Z.- Further, the exposure of each light sensitive layer 12 'can be effected in at least two stages during which light source 16 is disposed relative to face plate ll and mask 13 at the positions Z, and Z respectively. Alternatively, during the exposure of each light sensitive layer 12, the position of light source 16 relative to face plate ll and mask 13 can be changed continuously in the direction 2-2, for example, the light source 16 may be moved continuously from the position Z, through the position 2', to the position 2,.

When each light sensitive layer I2 is exposedin accordance with the present invention, as described above, the light indicated in solid lines at E on FIG. 6 passing through a relatively wide aperture in mask 13 at the central portion of the latter causes exposure of layer l2 over the width thereof indicated at I, when the light source In is disposed at the relative position Z,, the light passing through the relatively wide central aperture of the mask, and indicated by the broken-lines on FIG. 6, exposes layer 12 over a slightly greater width thereof indicated at t,. At the central portion of layer 12 the difference between the exposure widths t, and t, is very small, and may even be considered negligible, by reason of the fact that the distance between the light source positions Z, and Z is small when compared with the distances of the light source positions Z, and Z, from the mask 13. On FIG. 8, the curves III and IV respectively represent the light energy distributions on the region of the light sensitive layer 12 exposed to light passing through a relatively wide aperture at the central portion of mask 113 with the light source l6 disposed at the positions Z, and Z respectively, as on FIG. 6. Once again, the line a on FIG. 8 represents the threshhold light energy required for hardening of the light sensitive layer 112 and it will be apparent that, with the light energy distributions III and IV, the light sensitive layer will be hardened in an area having the width S On the other hand, as shown on FIG. 7, light from source 16 disposed at the position Z, and indicated in solid lines at E on FIG. 7 will, in passing through a relatively narrow aperture in an edge portion of mask 13, expose a region of light sensitive layer 112 having the width t However, when source 16 is moved to the position Z, on FIG. 5 during the exposure of layer 112, the light from such source passing through the relatively narrow aperture in the edge portion of mask 13, as indicated by the broken lines at E on FIG. 7, will pass through the mask aperture at a substantially different angle and therefore will impinge on a region of layer l2 that is displaced or shifted outwardly relatively to the area at which the light impinged on layer 12 when the source was at the position 2,. Thus, when light source 16 is disposed at positions Z, and Z during exposure of light sensitive layer l2, light passing through a relatively narrow aperture in the edge portion of mask 13 may be made to expose a region of layer l2 having the width t (FIG. 7) which is approximately equal to the width 1 (FIG. ti) over which a region of the layer 12 is exposed to light passing through a relatively wide aperture in the central portion of mask 13.

It will be seen from FIG. 9 that the light energy distributions on light sensitive layer 12 resulting from light passing through a relatively narrow aperture in the edge portion of mask 13 in the directions indicated at E and E on FIG. 7, and which are respectively represented by the curves V and VI, are similar to, and laterally displaced from each other so that the combined curves V and VI exceed the threshhold light energy a over the width 8,, that may be made equivalent to-the width S on FIG. 8. Thus, by exposing the light sensitive layer 12 in accordance with the present invention, that is, during the disposition of light source 16 at least at the two positions Z and Z the hardened regions of the light sensitive layer, and hence the phosphor stripes that result upon developing-of the layer, can be given substantially the same width 8,, at the central and edge portions of such layer.

Since shifting of the light source between the positions Z and Z is relied upon, in accordance with this invention, to ensurethat light passing through a relatively narrow aperture in an edge portion of mask 13 will result in hardening of the light sensitive layer over the width 5,, which is substantially greater than the width of the respective aperture, there is no need to provide the optical filter 15 with a relatively large gradient between its transmission characteristics at the central and edge portions of the filter. Thus, a light source of relatively lower light energy output, or a relatively shorter exposure time, can be employed to achieve the light energy distributions represented by the curves III, IV, V and VI on FIGS. 8 and 9. Further, it will be seen that the light energy distribution curves V and VI on FIG. 9, as well as the curves III and IV on FIG. 8, have relatively steep slopes at the threshhold light energy a,,. Thus, the hardened regions of the layer 12 that result from light passinig through relatively narrow apertures in edge portions of mask 13, as well as through the relatively wide central apertures, will be sharply and smoothly defined to ensure that the resulting phosphor stripes of the phosphor screen are similarly sharply and smoothly defined.

Of course, the extent to which the movement'of light source 16' from position Z to position Z is effective to increase the width of the area of layer 12 exposed to light passing through a particular aperture of mask 13 will depend upon the extent of the light source movement, that is, the distance between positions Z and Z and also on the distance from the. center of the face plate 11 to the mask aperture being considered. For example, on the graph of FIG. 12, the ordinates represent the ratio of the total width of the area of the light sensitive layer which is exposed to light when the light source is moved between the positions Z and Z relative to the width of the area exposed to light when the light source is disposed at a single position, and the abscissas represent the distances between the light source positions Z and Z Further, on FIG.12, the lines a, b

and c indicate the relationship of the distance between the light source positions Z and Z and the previously mentioned ratio of exposure widths at locations on the face plate that are at different distances x from the center thereof. Thus, the line a illustrates the described relationship at the center of the face plate, the line c represents the relationship at the edge of the face plate, that is, where the distance x=l80 mm., and the line b represents the relationship at an intermediate position, that is, where the distance x==l00 mm. It will be apparent from the foregoing that, by suitably considering the rate at which the widths of the apertures in the mask decrease-from the center to the edge portions of the mask and the ratio exposure width increase, as indicated on FIG. 12, the distance through which the light source is moved between the positions Z, and Z in the course of the exposure of the light sensitive layer can be selected to ensure that the resulting phosphor stripes will be ofa uniform, predetermined width over the entire extent of the phosphor screen. For example, in a particular example of the present invention, the phosphor screen of a color picture tube is optically printed using a grid mask of the type shown on FIG. 2 in which the pitch P between the apertures is 0.75 mm. and the apertures have graduated widths ranging from a maximum width W of 0.13 mm. at the center of the mask to a minimum width W -of 0.09 mm. at the edge portion of the mask. With the mask having the foregoing dimensions, each light sensitive layer is exposed to light therethrough from a light source which, in the course of the exposure, is disposed in two positions Z and Z having a distance of 2.0 mm. therebetween. In this example, after developing of each light sensitive layer, the resulting phosphor stripes are found to have a uniform width of approximately 0.25 mm. over the entire extent of the face plate.

Of course, in producing the phosphor screen of a color picture tube in accordance with this invention, the previously described steps,, that is, coating the face plate with a light sensitive layer, exposing such layer to a light source while the latter is at least at the two positions Z, and Z and then developing the exposed light sensitive layer, are repeated three times using light sensitive layers respectively containing phosphor materials having red, green and blue emissions. Further, it will be apparent that the positions Z and Z of the light source for exposing each of the three light sensitive layers are displaced in directions parallel to the surface of the face plate from the respective positions of the light source for exposing the other light sensitive layers.

It is also to be noted that, when the apertures in the mask are elongated and parallel to each other, as on FIG. 2, so that the resulting phosphor screen is made up of stripe-like areas of the different phosphors arranged in triads, the light source 16 to be disposed at least at the two positions Z and Z during the exposure of each light sensitive layer is preferably an elongated light source, for examle, an elongated mercury lamp, having its longitudinal axis extending parallel to the longitudinal axes of the apertures in the mask.

As shown on FIG. 11, an alternative form of mask 19 that can be used in producing the phosphor screen of acolor picture tube in accordance with this invention may include bridging elements 17 which extend across the parallel elongated apertures 18 at spaced apart locations along the latter which are preferably staggered in adjacent apertures for stabilizing, that is, increasing the resistance to vibration of the elements of the shadow grid between which the elongated apertures are defined. When the light source 16 is elongated, as described above, the bridging elements will not interfere with the exposure of continuous stripe-like areas of each light sensitive layer so that, upon development of each layer, continuous phosphor stripes will be produced.

Referring now to FIG. 10, it will be seen that an apparatus 20 suitable for use in exposing the successive light sensitive layers applied to'the surface of a face plate 22 during the production of the phosphor screen thereon in accordance with this invention includes a housing having clamp devices 23 for securely positioning the face plate 22 and associated shadow grid or mask 21 over an opening in the housing after a light sensitive layer has been applied to the face plate. The light source 24, which is elongated in the case when the apertures of grid 21 are elongated, is mounted within the housing on a mount made up of parts 25 and 26 respectively fixed to the light source and to the housing and being suitably movable relative toeacli other, for example, by either hydraulically or electrically operated actuators (not shown) of conventional design, so that light source 24 is movable relative to the clamped grid 21 and face plate 22 both in the direction of the arrow X and in the direction of the arrow Z. Further, within the housing there are suitably supported the corrective lens 27 and the filter 28 which correspond to the elements 14 and referred to in connection with FIG. 5. It will be apparent that relative movement of the mounting parts and 26 in the direction of arrow X serves to move light source 24 generally parallel to the surface of face plate 22 so as to dispose the light source either at the position shown in full lines, or in either of the positions shown in broken lines on FIG. 10. Such movement of the light source adapts the apparatus for exposure of the successively applied light sensitive layers intended to form the phosphor strips having green, red and blue emissions. During the exposure of each of the light sensitive layers, the mounting parts 25 and 26 are moved relative to each other in the direction of the arrow Z, thereby to displace the light source 24 in the direction parallel to a perpendicular to the center of face plate 22, for example, between the positions Z and Z on FIG. 5.

Although illustrative embodiments of the invention have been described in detail herein with reference to the drawings, it is to be understood that the invention is not limited to those precise embodiments, and that various changes and modifications may be effected therein by one skilled in the art without departing from the scope or spirit of the invention.

What is claimed is:

1. A method for producing the phosphor screen of a cathode ray tube comprising the steps of coating the surface of a face plate with a light sensitive layer containing phopshor material, exposing said layer to light passing through apertures of a mask from a light source which, in the course of said exposing of said layer to the light therefrom, isdisposed at least at two positions relative to said face plate, which two positions lie on, and are spaced from each other along a line parallel to a line perpendicular to said face plate at the center of the latter so that the areas of said layer exposed to light from said source through apertures of said mask adjacent the periphery of the latter will be larger relative to the respective apertures than are the areas of said layer exposed to light from said source through apertures of said mask adjacent said center of the latter, and developing said light sensitive layer so that said phosphor material will remain only on selected areas of said surface corresponding to said areas of said layer exposed to light through said apertures.

2. The method according to claim 1; in which said light source is moved continuously along said line from one of said two positions to the other of said position during said exposing of the light sensitive layer to light from said source.

3. The method according to claim 1; in which said exposing of the light sensitive layer to light from said source is effected in at least two stages with said source at one of said two positions and at the other of said positions, respectively.

4. The method according to claim 1; in which said mask is positioned adjacent to the face plate and said apertures are elongated.

5. The method according to claim 4; in which said elongated apertures extend parallel to each other and said light source is elongated and arranged parallel to the longitudinal axes of said elongated apertures.

6. The method according to claim 1; in which said phosphor material is adapted, when energized, to emit light of a predetermined color; and in which said steps are repeated with a second light sensitive layer containing phosphor material adapted, when energized, to emit light of another color, and with said at least two positions of the light source relative to the face plate for the exposing of said second layer to light therefrom being displaced, in a direction parallel to said surface of the face plate, from said at least two positions of the light source for exposing of the'first mentioned layer so that, upon the developing of said second layer, the respective phosphor material remains only on selected areas of said face plate which are displaced from said selected areas on which the phosphor material of said first layer remain.

7. The method according to claim 1; in which said mask is positioned adjacent to the face plate, and said apertures of the mask are elongated with their longitudinal axes parallel to each other and with the widths of the elongated apertures decreasing progessively toward the opposite edges of the mask from a maximum width at the center of the mask.

A method of producing the phosphor screen of a color picture tube comprising the steps of coating the surface of a faceplate with a first light sensitive layer containing phosphor material which is cathodoluminescent to have emissions of a predetermined color, positioning a mask adjacent said surface of the faceplate with said mask having elongated apertures which are parallel to each other and with the widths of said apertures being at a maximum adjacent the center of the mask and decreasing progressively toward the edges of said mask in the direction transverse to the longitudinal axes of the apertures, exposing said layer to light passing through said apertures from an elongated light source extending parallel to said longitudinal axes of the apertures, in the course of said exposing of the layer to the light from said source, disposing said source at least at two positions relative to said face plate which two positions lie on, and are spaced from each other along a line parallel to a line perpendicular to said face plate at the center thereof so that the elongated areas of said layer exposed to light from said source through said apertures adjacent the edges of the mask have greater widths relative to the respective apertures than the elongated areas of said layer exposed to light from said source through the apertures adjacent said center of the mask, and developing said light sensitive layer so that said phosphor material remains permanently on first stripe-like areas of said surface corresponding to said elongated areas of said layer exposed to light through said elongated apertures; and repeating said steps at least once with a second light sensitive layer containing phosphor material which is cathodoluminescent to have emissions of another color, and with said at least two positions of the light source relative to the face plate for the exposing of said second layer to light therefrom being displaced, in said direction transverse to the longitudinal axes of the mask apertures, from said at least two positions of the light source for exposing said first layer so that, upon the developing of said second layer, the respective phosphor material remains permanently on second stripe-like areas of said surface which are in side-by-side relation to said first stripe-like areas.

9. The method according to claim 8; in which said face plate and mask are fixedly positioned and said light source is moved relative to said face plate and mask for disposition of said light source at said at least two positions for each of the sequences of said steps.

10. The method according to claim 8; in which, during the exposing of each of said first and second light sensitive layers to light from said source the relative movement of said source and face plate between the respective at least two positions is effected continuously.

11. The method according to claim 8; in which the exposing of each of said first and second layers is effected in at least two stages with said light source disposed relative to said face plate at one of said two positions and at the other of said two positions, respectively. 

1. A METHOD FOR PRODUCING THE PHOSPHOR SCREEN OF A CATHODE RAY TUBE COMPRISING THE STEPS OF COATING THE SURFACE OF A FACE PLATE WITH A LIGHT SENSITIVE LAYER CONTAINING PHOSHOR MATERIAL, EXPOSING SAID LAYER TO LIGHT PASSING THROUGH APERTURES OF A MASK FROM A LIGHT SOURCE WHICCH, IN THE COURSE OF SAID EXPOSING OF SAID LAYER TO THE LIGHT THEREFROM, IS DISPOES AT LEAST TWO POSITIONS RELATIVE TO SAID FACE PLATE, WHICH TWO POSITIONS LIE ON, AND ARE SPACED FROM EACH OTHER ALONG A LINE PARALLELEL TO A LINE PERPENDICULAR TO SAID FACE PLATE AT THE CENTER OF THE LATTER SO THAT THE AREAS OF SAID LAYER EXPOSED TO LIGHT FROM SAID SOURCE THROUGH APERTURES OF SAID MASK ADJACENT THE PERIPHERY OF THE LATTER WILL BE LARGER RELATIVE TO THE PROSPECTIVE APERTURES THAN ARE THE AREAS OF SAID LAYER ECXOSED TO LIGHT FROM SAID SOURCE THROUGH APERTURES OF SAID MASK ADJACENT SAID CENTER OF THE LATTER, AND DEVEPOING DAIS LIGHT SENSITIVE LAYER SO THAT SIAD PHOSPHOR ,ATERIAL WILL REMAIN ONLY ON SELECTED AREAS OF SAID SURFACE CORRESPONDING TO SAID AREAS OF SAID LAYER EXPOSED TO LIGHT THROUGH SAID APERTURES.
 2. The method according to claim 1; in which said light source is moved continuously along said line from one of said two positions to the other of said position during said exposing of the light sensitive layer to light from said source.
 3. The method according to claim 1; in which said exposing of the light sensitive layer to light from said source is effected in at least two stages with said source at one of said two positions and at the other of said positions, respectively.
 4. The method according to claim 1; in which said mask is positioned adjacent to the face plate and said apertures are elongated.
 5. The method according to claim 4; in which said elongated apertures extend parallel to each other and said light source is elongated and arranged parallel to the longitudinal axes of said elongated apertures.
 6. The method according to claim 1; in which said phosphor material is adapted, when energized, to emit light of a predetermined color; and in which said steps are repeated with a second light sensitive layer containing phosphor material adapted, when energized, to emit light of another color, and with said at least two positions of the light source relative to the face plate for the exposing of said second layer to light therefrom being displaced, in a direction parallel to said surface of the face plate, from said at least two positions of the light source for exposing of the first mentioned layer so that, upon the developing of said second layer, the respective phosphor material remains only on selected areas of said face plate which are displaced from said selected areas on which the phosphor material of said first layer remain.
 7. The method according to claim 1; in which said mask is positioned adjacent to the face plate, and said apertures of the mask are elongated with their longitudinal axes parallel to each other and with the widths of the elongated apertures decreasing progessively toward the opposite edges of the mask from a maximum width at the center of the mask.
 8. A method of producing the phosphor screen of a color picture tube comprising the steps of coating the surface of a faceplate with a first light sensitive layer containing phosphor material whiCh is cathodoluminescent to have emissions of a predetermined color, positioning a mask adjacent said surface of the faceplate with said mask having elongated apertures which are parallel to each other and with the widths of said apertures being at a maximum adjacent the center of the mask and decreasing progressively toward the edges of said mask in the direction transverse to the longitudinal axes of the apertures, exposing said layer to light passing through said apertures from an elongated light source extending parallel to said longitudinal axes of the apertures, in the course of said exposing of the layer to the light from said source, disposing said source at least at two positions relative to said face plate which two positions lie on, and are spaced from each other along a line parallel to a line perpendicular to said face plate at the center thereof so that the elongated areas of said layer exposed to light from said source through said apertures adjacent the edges of the mask have greater widths relative to the respective apertures than the elongated areas of said layer exposed to light from said source through the apertures adjacent said center of the mask, and developing said light sensitive layer so that said phosphor material remains permanently on first stripe-like areas of said surface corresponding to said elongated areas of said layer exposed to light through said elongated apertures; and repeating said steps at least once with a second light sensitive layer containing phosphor material which is cathodoluminescent to have emissions of another color, and with said at least two positions of the light source relative to the face plate for the exposing of said second layer to light therefrom being displaced, in said direction transverse to the longitudinal axes of the mask apertures, from said at least two positions of the light source for exposing said first layer so that, upon the developing of said second layer, the respective phosphor material remains permanently on second stripe-like areas of said surface which are in side-by-side relation to said first stripe-like areas.
 9. The method according to claim 8; in which said face plate and mask are fixedly positioned and said light source is moved relative to said face plate and mask for disposition of said light source at said at least two positions for each of the sequences of said steps.
 10. The method according to claim 8; in which, during the exposing of each of said first and second light sensitive layers to light from said source the relative movement of said source and face plate between the respective at least two positions is effected continuously.
 11. The method according to claim 8; in which the exposing of each of said first and second layers is effected in at least two stages with said light source disposed relative to said face plate at one of said two positions and at the other of said two positions, respectively. 